As another poster mentioned, memes are analogous to viruses in their interaction with humans. I would hazard to guess that any survival value to humans is purely accidental, especially taking into account the time frames involved.
Certainly they do, and perhaps before the internet, a larger proportion of memes were of the useful type. For whatever reason, post-internet, memes are no longer reliant on having survival value to humans in order to propagate. Note that the converse is not true.
